Generating Steam Turbine Performance Maps

ABSTRACT

In some aspects, a steam turbine system includes a high-pressure turbine section; a low-pressure turbine section; a high-pressure control valve operable to provide an adjustable flow of steam into the high-pressure turbine section; a low-pressure control valve operable to provide an adjustable flow of steam into the low-pressure turbine section; a controller associated with the high-pressure control valve and the low-pressure control valve. The controller is operable to: receive measurements of three or more different operating points of the steam turbine system, the measurements of each of the three or more different operating points including a position of the high-pressure control valve, a position of the low-pressure control valve, and two of process variables of the steam turbine system; calculate coefficients of a steam performance map of the steam turbine system based on the measurements; and generate the steam performance map based on the coefficients.

BACKGROUND

This specification relates to generating a performance map of a steamturbine system.

A steam turbine system can extract thermal energy from pressurized steamand use the energy to do mechanical work on a rotating output shaft, forexample, to drive an electrical generator. The steam turbine can usemultiple stages in the expansion of the steam such that steam can beadmitted or extracted before the last stage, for example, to improvethermodynamic efficiency.

SUMMARY

In some aspects, a steam turbine system includes a high-pressure turbinesection; a low-pressure turbine section; a high-pressure control valveoperable to provide an adjustable flow of steam into the high-pressureturbine section; a low-pressure control valve operable to provide anadjustable flow of steam into the low-pressure turbine section; acontroller associated with the high-pressure control valve and thelow-pressure control valve, the controller operable to: receivemeasurements of three or more different operating points of the steamturbine system, the measurements of each of the three or more differentoperating points including a position of the high-pressure controlvalve, a position of the low-pressure control valve, and two of processvariables of the steam turbine system; calculate coefficients of a steamperformance map of the steam turbine system based on the measurements ofeach of the three or more different operating points, the steamperformance map representing a first relationship between the positionof the high-pressure control valve and the two of the process variablesof the steam turbine system, and a second relationship between theposition of the low-pressure control valve and the two of the processvariables of the steam turbine system; and generate the steamperformance map of the steam turbine system based on the coefficients.

In some implementations, the controller is further operable to: receivecurrent values of the two of the process variables of the steam turbinesystem; determine a desired position of the high-pressure control valveand a desired position of the low-pressure control valve based on thecoefficients of the steam performance map of the steam turbine systemand the current values of the two of the process variables of the steamturbine system; output the desired position of the high-pressure controlvalve to a first actuator coupled with the high-pressure control valve;and output the desired position of the low-pressure control valve to asecond actuator coupled with the low-pressure control valve.

In some implementations, the steam turbine system further includes anumber of sensors for measuring the two of the process variables of thesteam turbine system.

In some implementations, the process variables of the steam turbinesystem include two or more of the following: turbine speed, turbineload, extraction or admission pressure or flow, inlet steam pressure orflow, and exhaust steam pressure or flow of the steam turbine system.

In some implementations, the low-pressure turbine section is a firstlow-pressure turbine section; and the low-pressure control valve is afirst low-pressure control valve, the steam turbine system including oneor more low-pressure turbine sections in addition to the firstlow-pressure turbine section and one or more low-pressure control valvesin addition to the first low-pressure control valve.

In some implementations, the controller is operable to calculate thecoefficients of a steam performance map of the steam turbine system bycurve fitting the measurements of the three or more different operatingpoints.

In some implementations, the steam turbine system operates in anextraction mode or an admission mode.

In some aspects, a method for generating a steam performance map of asteam turbine system includes: receiving, by data processing apparatus,measurements of three or more different operating points of the steamturbine system, the measurements of each of the three or more differentoperating points including a position of the high-pressure controlvalve, a position of the low-pressure control valve, and two of processvariables of the steam turbine system; calculating, by the dataprocessing apparatus, coefficients of a steam performance map of thesteam turbine system based on the measurements of each of the three ormore different operating points, the steam performance map representinga first relationship between the position of the high-pressure controlvalve and the two of the process variables of the steam turbine system,and a second relationship between the position of the low-pressurecontrol valve and the two of the process variables of the steam turbinesystem; and generating, by the data processing apparatus, the steamperformance map of the steam turbine system based on the coefficients.

In some implementations, the method further includes controlling thesteam turbine system based on the steam performance map of the steamturbine system.

In some implementations, the controlling the steam turbine system basedon the steam performance map of the steam turbine system includes:receiving current values of the two process variables of the steamturbine system; determining a desired position of the high-pressurecontrol valve and a desired position of the low-pressure control valvebased on the coefficients of the steam performance map of the steamturbine system and the current values of the two process variables ofthe steam turbine system; outputting the desired position of thehigh-pressure control valve to an actuator coupled with thehigh-pressure control valve; and outputting the desired position of thelow-pressure control valve to an actuator coupled with the low-pressurecontrol valve.

In some implementations, the method further includes: operating thesteam turbine system at the three or more different operating points;and for the each of the three or more different operating points,measuring the position of the high-pressure control valve, the positionof the low-pressure control valve, and the two of the process variablesof the steam turbine system.

In some implementations, the process variables of the steam turbinesystem include two or more of the following: turbine speed, turbineload, extraction or admission pressure or flow, inlet steam pressure orflow, and exhaust steam pressure or flow of the steam turbine system.

In some implementations, one of the two of the process variables of thesteam turbine system includes a turbine load or a turbine speed, andanother of the two of the process variables of the steam turbine systemincludes an extraction pressure or flow of the steam turbine system.

In some implementations, the calculating coefficients of a steamperformance map of the steam turbine system includes calculating thecoefficients of a steam performance map of the steam turbine system bycurve fitting the measurements of each of the three or more differentoperating points.

In some aspects, a non-transitory computer-readable medium storesinstructions that, when executed by data processing apparatus, performoperations for generating a steam performance map of a steam turbinesystem that includes a high-pressure control valve operable to providean adjustable flow of steam fluid into a high-pressure turbine sectionand a low-pressure control valve operable to provide an adjustable flowof steam fluid into a low-pressure turbine section. The operationsinclude: receiving, by data processing apparatus, measurements of threeor more different operating points of the steam turbine system, themeasurements of each of the three or more different operating pointsincluding a position of the high-pressure control valve, a position ofthe low-pressure control valve, and two of process variables of thesteam turbine system; calculating, by the data processing apparatus,coefficients of a steam performance map of the steam turbine systembased on the measurements of each of the three or more differentoperating points, the steam performance map representing a firstrelationship between the position of the high-pressure control valve andthe two of the process variables of the steam turbine system, and asecond relationship between the position of the low-pressure controlvalve and the two of the process variables of the steam turbine system;and generating, by the data processing apparatus, the steam performancemap of the steam turbine system based on the coefficients.

In some implementations, the operations further include controlling thesteam turbine system based on the steam performance map of the steamturbine system.

In some implementations, the controlling the steam turbine system basedon the steam performance map of the steam turbine system includes:receiving current values of the two process variables of the steamturbine system; determining a desired position of the high-pressurecontrol valve and a desired position of the low-pressure control valvebased on the coefficients of the steam performance map of the steamturbine system and the current values of the two process variables ofthe steam turbine system; outputting the desired position of thehigh-pressure control valve to an actuator coupled with thehigh-pressure control valve; and outputting the desired position of thelow-pressure control valve to an actuator coupled with the low-pressurecontrol valve.

In some implementations, the operations further include: operating thesteam turbine system at the three or more different operating points;and for the each of the three or more different operating points,measuring the position of the high-pressure control valve, the positionof the low-pressure control valve, and the two of the process variablesof the steam turbine system.

In some implementations, the process variables of the steam turbinesystem include two or more of the following: turbine speed, turbineload, extraction or admission pressure or flow, inlet steam pressure orflow, and exhaust steam pressure or flow of the steam turbine system.

In some implementations, the calculating coefficients of a steamperformance map of the steam turbine system includes calculating thecoefficients of a steam performance map of the steam turbine system bycurve fitting the measurements of each of the three or more differentoperating points.

The details of one or more implementations are set forth in theaccompanying drawings and the description below. Other features,objects, and advantages will be apparent from the description anddrawings, and from the claims.

DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic diagram of an example extraction steam turbinesystem.

FIG. 2 is a plot illustrating an example original equipment manufacturer(OEM) steam performance map.

FIG. 3 is a plot illustrating an example steam map of an extractionsteam turbine system generated according to example techniques describedin this disclosure.

FIG. 4 is a schematic diagram illustrating an example steam turbinecontrol circuit that includes functions blocks of a controller of asteam turbine system.

FIG. 5 is a flow diagram illustrating an example process for generatinga steam map of a steam turbine system.

FIG. 6 is a plot illustrating another example steam map of an extractionsteam turbine system generated according to example techniques describedin this disclosure.

DETAILED DESCRIPTION

A steam turbine can be configured to operate in an extraction mode(referred to as an extraction steam turbine), an admission mode(referred to as an admission steam turbine), or an alternating modewhere the steam turbine alternates between an extraction mode and anadmission mode. In an extraction steam turbine, steam can be extractedfrom a turbine before the steam flows through the last stage. In anadmission steam turbine, steam can be admitted to a turbine before thesteam flows through the last stage. In an extraction/admission steamturbine, steam can be admitted or extracted to the turbine before thesteam flows through the last stage. In some implementations, steamturbines can include more than one extraction/admission line.

As an example, an extraction turbine extracts steam from an intermediatestage of a steam turbine, and supplies the steam to a process systemsuch as a plant for use. For example, an extraction steam turbine mayinclude a high-pressure (HP) section and a low-pressure (LP) section.Steam enters the extraction steam turbine through a high-pressure inletcontrol valve and expands through the high-pressure section of theturbine, losing both pressure and temperature, as the steam energy isconverted to the mechanical power transmitted by the steam turbineshaft. Steam is extracted from the turbine at an intermediate stage ofthe steam turbine and can be used for various plant processes. The steamthat is not extracted flows through a low-pressure control valve to thelow-pressure section of the extraction steam turbine and continues toexpand, converting the steam energy into shaft power. The shaft of theturbine can be common to both the high-pressure and low-pressure turbinesections.

Similarly, in some implementations, an admission steam turbine includesa high-pressure turbine section and a low-pressure turbine section.Steam enters the turbine through the high-pressure inlet control valveand expands through the high-pressure section of the turbine, losingboth pressure and temperature, as the steam energy is converted to themechanical power transmitted by the steam turbine shaft. Additionalsteam can be admitted into the admission turbine at an intermediatestage of the steam turbine and may be supplied from various plantprocesses. The admitted steam flows through the low-pressure controlvalve to the low-pressure section of the turbine, where the admittedsteam is combined with the steam flow from the high-pressure section.The combined steam expands through the low-pressure section of theturbine where the steam energy is converted into shaft power. The shaftof the turbine can be common to both the high-pressure and low-pressuresections.

In some implementations, a steam turbine can be configured to alternatebetween extracting steam and admitting steam based on plant conditions.While the steam turbine extracts steam, the steam that is not extractedflows through the low-pressure control valve to the low-pressure sectionof the turbine where it continues to expand, converting the steam energyinto shaft power. When the steam turbine admits steam, the admittedsteam flows through the low-pressure control valve to the low-pressuresection of the turbine, where it combines with the steam flow from thehigh-pressure section and expands through the low-pressure section ofthe turbine, converting the steam energy into shaft power. The shaft ofthe turbine can be common to both the high-pressure and low-pressuresections.

In the following, a steam turbine system configured to operate in anextraction only, admission only, or extraction or admission mode iscollectively referred to as an extraction or admission steam turbine,unless otherwise specified.

Extraction or admission steam turbines are generally controlled withMulti-Input Multi-Output (MIMO) ratio-limiting electronic controlsystems. In some implementations, the extraction or admission steamturbine system includes two process variables (also referred to ascontrollable parameters): extraction or admission pressure/flow andturbine speed/load. The parameters can be controlled through thepositions of the HP and LP control valves. The relationship of valvepositions to extraction or admission flow and turbine power is typicallyprovided by a turbine original equipment manufacturer (OEM), at ratedconditions, in a steam performance map. In the case of extractionturbines with more than one LP valve, a performance map for each LPstage is typically provided. In some implementations, the performancemap can represent the relationship between two or more of speed/load andextraction pressure, inlet and extraction pressure, inlet and exhaustpressure, etc. In some implementations, the performance map can also bemulti-dimensional. For example, the performance map can include threevariables such as speed, extraction pressure, and exhaust pressure ifthere are two extraction lines.

In some implementations, each controllable parameter has an associatedproportional-integral-derivative (PID) controller. For example, theextraction steam turbine system can include a Speed/Load PID controllerand extraction Flow/Pressure PID controller; the admission steam turbinesystem can include a Speed/Load PID controller and admissionFlow/Pressure PID controller. In some implementations, a change in theHP valve position has an effect on both the turbine speed/load as wellas the extraction pressure/flow. Similarly, a change in the LP valveposition may result in a change to both turbine speed/load as well asthe extraction pressure/flow. In some implementations, the output ofeach PID controller is used to determine the HP and LP opening degreesin order to regulate the steam flow through each section of the turbine.

The relationship between outputs of the PID controller and the resultingvalve positions can be given by a steam performance map. For example,according to the steam performance map, a change in the speed controloutput of the Speed/Load PID controller can result in respective changesin the HP and LP valve positions such that the extraction pressureremains constant while the turbine speed/load changes. Similarly,according to the steam performance map, a change in the extractioncontrol output can result in respective changes in the HP and LP valvepositions such that turbine speed/load remains constant while theextraction pressure changes.

For an optimal performance, the extraction or admission turbinecontroller needs an accurate steam performance map which matches theextraction or admission turbine system it is controlling. An accuratesteam performance map decouples the influence of one controller outputon the other process input in the MIMO system. Over time, ratedconditions for the turbine may change; turbines and valves may beoverhauled; or generators or compressors may be replaced or overhauled,resulting in changes in the overall system dynamics and new relationshipof the valve position versus the flow. Consequently, the original OEMspecified map may no longer match the underlying extraction or admissionturbine system. Degradation of control quality can occur when theelectronic controller of the extraction or admission turbine systemremains programmed with the original OEM specified map. Errors in theextraction or admission turbine system can lead to instability andrequire de-tuning of PID dynamics to reduce the interaction of thecontrol loops.

This disclosure provides steam map discovery or generation techniquesfor generating a steam map based on actual responses and performances ofthe underlying extraction or admission steam turbine system. Rather thanmerely modifying an existing OEM steam map, a new steam performance mapis created based on measurements of the system responses and thegenerated steam map can reflect actual plant conditions. As such, moreaccurate, effective control of the steam turbine system can be achieved.For example, the steam map generation techniques include changing thespeed/load demand and monitoring both the speed/load and the pressuresignals in response to the changing of the speed/load demand, and thenchanging the pressure demand and monitoring both the speed/load andpressure signals in response to the changing of the pressure demandagain. From speed/load and pressure signal responses, both thespeed/load of the responses and the amount of responses, a steam map canbe generated. By changing each signal demand and measuring the responseof both signals, the relationship between the turbine speed/load andextraction processes can be learned, based on the actual systemresponses, such that they can be de-coupled, rather than deducing therelationship from the predetermined OEM steam map provided by themanufacturer. By measuring the system responses and determining therelationship of the actual system, a more accurate steam performance mapcan be obtained based upon specific end-user site conditions.

In some implementations, the steam map generation techniques can beutilized by commissioning engineers for improving the performance of anyextraction turbine already installed in the field. For example, thesteam map generation techniques allow operators to verify or otherwiseassess the OEM steam map provided for new installations or updated steammaps, as a result of site system changes or a turbine overhaul. In someimplementations, the described steam map generation techniques can beexecuted periodically or from time to time (e.g., as frequently asnecessary) to adjust for changes in the extraction or admission steamturbine system.

In some implementations, the steam map generation techniques can useprocess variables or parameters other than the turbine speed/load andextraction or admission pressure/flow. For example, for the threeoperating modes discussed above (i.e., extraction only, admission only,and alternating mode), there are at least four process variables orcontrollable parameters that can be used to generate a steam map:speed/load, extraction or admission pressure/flow, inlet steampressure/flow, and exhaust steam pressure/flow. A single extractionsteam turbine system can include two or more control valves, forexample, an HP and at least one LP control valves. Therefore, any two ormore (depending on the number of control valves) of the four processvariables can be controlled at one time. For example, three processvariables can be controlled at one time if there are three controlvalves in the extraction stream turbine system. In some implementations,six combinations of the process variables can be used as controllableparameters for generating the steam performance map. Each of thecombination is referred to as Mode 0 to Mode 5 as below:

Mode 0=Speed/load and Extraction pressure/flowMode 1=Speed/load and Inlet pressure/flowMode 2=Extraction pressure/flow and Inlet pressure/flowMode 3=Speed/load and Exhaust pressure/flowMode 4=Exhaust pressure/flow and Extraction pressure/flowMode 5=Inlet pressure/flow and Exhaust pressure/flow

While Mode 0 is discussed in the following as an example, the steam mapgeneration techniques described in this disclosure can be used for anyother control parameter combinations, such as the combinations in Mode1-5. The steam performance map is indifferent to the actual processvariables that are actively being controlled by the controller in thevarious modes.

FIG. 1 is a schematic diagram of an example extraction steam turbinesystem 100. The extraction steam turbine system 100 includes anextraction steam turbine 110 that is coupled with a controller 150. Theextraction steam turbine 110 includes two control valves, the HP controlvalve 145 and the LP control valve 135, which control the steam flow.The extraction steam turbine 110 includes two actuators 125 and 115which use mechanical linkages to control the inlet control valve (i.e.,the HP control valve 145) and extraction control valve (i.e., the LPcontrol valve 135), respectively. The extraction steam turbine system100 can include one or more sensors (not shown) for measuring one ormore process variables (e.g., speed/load, extraction or admissionpressure/flow, inlet steam pressure/flow, and exhaust steampressure/flow) of the extraction steam turbine system 100. One or moreprocess variables can be used as control loop input to the controller,for example, for real-time control of the extraction steam turbinesystem 100. The controller 150 can receive example control loop inputssuch as speed and pressure sensor inputs 122. The controller 150 outputscontrol output 142 to the actuator 125 for controlling the position ofthe HP control valve 145 and control output 132 to the actuator 115 forcontrolling the position of the LP control valve 135.

In the example steam turbine system 100 shown in FIG. 1, the twocontrollable parameters, Speed and Extraction, in Mode 0 refer to thespeed of the steam turbine shaft, and the extraction header pressure orflow of the steam turbine, respectively. The two controllableparameters, Speed and Inlet, in Mode 1 refer to the speed of the steamturbine, and the inlet header pressure or flow of the steam turbine,respectively. The two controllable parameters, Extraction and Inlet, inMode 2 refer to the extraction pressure or flow of the steam turbine,and the inlet header pressure or flow of the steam turbine,respectively. The two controllable parameters, Speed and Exhaust, inMode 3 refer to the speed of the steam turbine shaft, and the exhaustpressure or flow of the steam turbine, respectively. The twocontrollable parameters, Exhaust and Extraction, in Mode 4 can be referto the exhaust pressure or flow of the steam turbine, and the extractionheader pressure or flow of the steam turbine, respectively. The twocontrollable parameters, Inlet and Exhaust, in Mode 5 refer to the inletheader pressure or flow of the steam turbine, and the exhaust pressureor flow of the steam turbine, respectively. The measurement of turbinespeed, extraction pressure or flow, exhaust header pressure or flow,inlet header pressure or flow, can be obtained from transducers on theturbine. The signals from these transducers are wired to the control,shown in FIG. 1 as 122.

FIG. 2 is a plot illustrating an example original equipment manufacturer(OEM) steam performance curve 200 of a steam turbine system. Based onthe steam performance curve 210, which is typically provided by themanufacturer of the turbine, a turbine control operational envelope 220can be created, which is typically referred to as the steam performancemap 220. The X-axis 210 represents the turbine load (S) and the Y-axis230 represents the flow through the HP valve, which is typicallydirectly proportional to the position of the HP valve of the steamturbine system. In some implementations, the actual steam map from theOEM is defined in flows, which can be converted to position and pressurerelationships for the controller. As shown in FIG. 2, the steam),performance map 220 includes several vertices, Point A 215 (thatrepresents the maximum turbine load/power and HP valve flow with minimumextraction flow), Point B 225 (that represents the minimum turbineload/power and HP valve flow at maximum extraction flow and Point C 235(that represents the minimum turbine load/power and HP valve flow atminimum extraction flow).

FIG. 3 is a plot illustrating an example steam map 300 generatedaccording to the example steam map generation techniques. Rather thanbeing derived from the OEM steam performance map 220 as shown in FIG. 2(also shown in FIG. 3 for reference), the example steam map 300 iscreated based on actual measurements of an underlying steam turbinesystem (e.g., the example steam turbine system 100 in FIG. 1).Specifically, the example steam map 300 shows the relationship betweenthe Speed/Load PID controller and Extraction PID controller of anextraction steam turbine system.

The X-axis 310 represents the turbine power/load (S) and the Y-axis 320represents the position of the HP valve or the flow through that valve.Each of the circles (e.g., circle 306) is an operating point (determinedby its HP and LP positions). Besides Point A 215, Point B 225, Point C235, three other points are defined and denoted as solid dots: Point D345 represents the HP position at maximum turbine load/power at maximumLP position; Point E 355 represents the turbine load/power at maximum HPposition; and Point F 365 represents the LP position at maximum turbineload/power and maximum HP position. The lower limit of the LP valveposition is given as the diagonal line 330 from Point C 235 to Point B225 (Minimum LP Position). The upper limit of the LP valve position isgiven as the diagonal line 340 from Point A 215 to Point D 345 (MaximumLP Position). The “Constant P Line” (e.g., lines 332, 334, and 336)shows a constant extraction flow.

For a given operating point, a change in the demand of a PID controller(e.g., either from the Speed/Load PID controller or extractionFlow/Pressure PID controller) may result in respective movements of boththe HP value and LP valve. The movements of the operating point are suchthat the other process remains constant. For example, an increase inextraction PID demand moves the operating point (e.g., the operatingpoint 306) along a vertical line in the upwards direction to maintainconstant load. This is accomplished by increasing the HP demand anddecreasing the LP demand. The amount the HP and LP move as a result of achange in PID demand is referred to as “Ratioing.”

For example, as shown in FIG. 3, the arrows from operating point 306indicate the directions the operating point 306 will move for acorresponding change in a PID demand. For example, for an increase indemand from the Speed/Load PID, the operating point 306 moves in thedirection of the arrow 312. In this example, the Speed/Load PIDincreases the S demand, while the extraction PID demand remainsconstant, moving the operating point from 306 to 308. The ratio limiterincreases the HP demand by ΔHP and increases the LP demand by ALP. Theoperating point 306 achieves the increase in turbine load while theextraction process remains constant.

FIG. 4 is a schematic diagram illustrating an example steam turbinecontrol circuit 400 that includes functions blocks of a controller of asteam turbine system (e.g., the controller 150 of the steam turbinesystem 100). In a single extraction steam turbine, two process variablescan be controlled. As previously discussed, these process variables canbe any of the four process variables: turbine speed/load,extraction/admission pressure/flow, inlet pressure/flow, and exhaustpressure/flow. In FIG. 4, these two process variables denoted as “S” and“P.” Accordingly, the extraction steam turbine control circuit 400includes an S process and a P process. The extraction steam turbinecontrol circuit 400 includes a controller 405 that receives an S processinput 410 (Usually speed or load of the turbine). The S process input410 is input into a PID controller (denoted as S PID 420 in FIG. 4). Thecontroller 405 can also receive a P process input 415 (usuallyextraction pressure/flow but can be, for example, inlet pressure/flow,or the exhaust pressure/flow). The P process input 415 is input into adifferent PID controller (denoted as P PID 425 in FIG. 4). TheSpeed/Load PID controller 420 receives the S process input 410 andgenerates an S demand output (e.g., a Speed/Load PID Demand) that is fedinto a ratio limiter 450. Similarly, the Extraction PID controller 425receives the P process input 415 and generates a P demand output (e.g.,an Extraction PID demand) that is fed into the ratio limiter 450.

A ratio limiter can be used to reduce or limit interactions in a MIMOcontrol system. If one of the control outputs affects both of thecontrol inputs, the system is said to have interaction. Interaction canbe reduced or even eliminated by use of a steam map or a ratio-limiter.Ratio refers to applying scaling terms to the demands for each of thecontrol loops, such that each control loop controls both valves withminimal effect on the other control loop. A limiter refers to the casein which a valve or a control reaches its controlling limit.

The ratio limiter 450 in FIG. 4 can be used to reduce interactions inthe MIMO controller 405 that receives the S process output and P processoutput, and generates an HP actuator output 440 and a LP actuator output445. The ratio limiter 450 defines a relationship 430 among an HP valveposition (represented by the HP actuator output 440) and the S PIDdemand and the P PID demand, as well as the relationship 435 among a LPvalve position (represented by the LP actuator output 445) and the S PIDdemand and the P PID demand.

The relationships 430 and 435 are given by Equations (1) and (2),respectively:

HP=K1*S+K2*P+K3  (1)

LP=K4*S+K5*P+K6  (2)

In some implementations, the K values (i.e., K1, K2, K3, K4, K5, and K6)are derived from the OEM steam map (e.g., the OEM steam map 220 in FIG.2). Each K term can be determined based on given or known operationalpoints (e.g., the Point A 215, Point B 225, Point C 235 in FIG. 2) inthe OEM steam map, which are defined by the X axis (S) and Y axis (HP)values in the steam map. For example, the coordinates of Point A 215,Point B 225, Point C 235 can be given as:

A=(SA,HA)  (3)

B=(SB,HB)  (4)

C=(SC,HC)  (5)

K1 can be derived as:

$\begin{matrix}{{K\; 1} = \frac{{HA} - {HC}}{{SA} - {SC}}} & (6)\end{matrix}$

In this case, K1 represents the slope of the line from Point C 235 toPoint A 225, which gives the change in HP over the change in S, for aconstant P value. Similar derivations can be used to calculate K2-K6 interms of points A, B, and C.

In some implementations, the OEM steam map may not reflect the actualconditions of the underlying steam turbine system. In someimplementations, the K values (i.e., K1, K2, K3, K4, K5, and K6) arederived based on actual measurements of different operating points ofthe underlying steam turbine system. For example, an electroniccontroller can make system measurements by moving the steam turbinesystem to three or more different operating points and recordingmeasurements (e.g., the HP valve position, the LP valve position, theload, and the extraction pressure) of each of the three or moredifferent operating points.

FIG. 6 is a plot illustrating another example steam map 600 of anextraction steam turbine system generated according to exampletechniques described in this disclosure. As an example, let Hp1, Lp1,S1, and P1 denote the HP valve position, the LP valve position, theload, and the extraction pressure of a first operating point (601) ofthe steam turbine system. Similarly, let Hp2, Lp2, S2, and P2 be the HPvalve position, the LP valve position, the load, and the extractionpressure of a second operating point (602), respectively; and let Hp3,Lp3, S3, and P3 be the HP valve position, the LP valve position, theload, and the extraction pressure of a third operating point (603),respectively. The values of K1-K6 can be given by the below equations:

K3=[Hp3*P2−k1*S3*P2−Hp2*P3+k1*S2*P3]/(P2−P3)  (7)

K2=Hp2/P2−k1*S2/P2−(Hp3−k1*S3−Hp2*P3/P2+k1*S2*P3/P2)/(P2−P3)  (8)

K1=(Hp1*(P2−P3)+Hp2*(P3−P1)+Hp3*(P1−P2))/(S1*(P2−P3)+S2*(−P1+P3)+S3*(P1−P2))  (9)

K6=[Lp3*P2−k4*S3*P2−Lp2*P3+k4*S2*P3]/(P2−P3)  (10)

K5=Lp2/P2−k4*S2/P2−(Lp3−k4*S3−Lp2*P3/P2+k4*S2*P3/P2)/(P2−P3)  (11)

K4=(Lp1*(P2−P3)+Lp2*(P3−P1)+Lp3*(P1−P2))/(S1*(P2−P3)+S2*(−P1+P3)+S3*(P1−P2))  (12)

Once measurements have determined values for K1-K6, the Ratio-Limiterequations (e.g., the Equations (1) and (2)) are defined for thecontroller. In some implementations, in addition, points A, B, and C canbe reverse calculated in order to provide the steam map back to the userfor verification.

FIG. 5 is a flow diagram illustrating example process 500 for generatinga steam performance map of a steam turbine system. The steam turbinesystem can be an extraction and/or admission steam turbine system (e.g.,the steam turbine system 100 in FIG. 1). The steam turbine systemincludes, for example, a high-pressure turbine section, a low-pressureturbine section, a high-pressure control valve (e.g., the HP controlvalve 145) operable to provide an adjustable flow of steam into thehigh-pressure turbine section, a low-pressure control valve (e.g., theLP control valve 135) operable to provide an adjustable flow of steaminto the low-pressure turbine section, and a controller (e.g., thecontroller 150) for controlling positions of the high-pressure controlvalve and the low-pressure control valve. In some implementations, thelow-pressure turbine section is a first low-pressure turbine section;and the low-pressure control valve is a first low-pressure controlvalve. The steam turbine system can include one or more low-pressureturbine sections in addition to the first low-pressure turbine sectionand one or more low-pressure control valves in addition to the firstlow-pressure control valve. The controller can include one or more PIDcontrollers (e.g., the S PID controller 420 and the P PID controller425) for one or more process variables (e.g., speed/load, extraction oradmission pressure/flow, inlet steam pressure/flow, and exhaust steampressure/flow), a ratio limiter 450, and other data processingapparatus. The example process 500 can be performed by the controller oranother data processing apparatus (e.g., an on-site or remote computersystem). For example, the example process 500 can be performed by dataprocessing apparatus that receives turbine data stored in acloud/remote/edge server, for example, in the context of Internet ofThing (IoT) technology. In some implementations, generating a steamperformance map of a steam turbine system includes determining the ratiolimiter coefficients (e.g., constants K1-K6) of the ratio limiter of thecontroller of the steam turbine system. The generated steam performancemap can be received, stored or otherwise made available to thecontroller such that the controller controls the steam turbine systemaccording to the generated steam performance map.

At 510, measurements of three or more different operating points of thesteam turbine system are received. The measurements of each of the threeor more different operating points can include a position of thehigh-pressure control valve, a position of the low-pressure controlvalve, and two of process variables of the steam turbine system. In someimplementations, the measurements of the three or more differentoperating points are obtained by operating the steam turbine system atthe three or more different operating points under different operatingconditions; and for each of the three or more different operatingpoints, measuring the position of the high-pressure control valve, theposition of the low-pressure control valve, and the two of the processvariables of the steam turbine system. In some implementations, themeasurements of the different operating points can include additional ordifferent parameters. For example, the measurements of the differentoperating points can include a different combination of a position ofthe high-pressure control valve, a position of the low-pressure controlvalve, and process variables of the steam turbine system. Themeasurements can be received, for example, by receiving data directly orindirectly from sensors or other measuring or monitoring devices of thesteam turbine system in real time or substantially real time, byretrieving historic data or records of the sensors or other measuring ormonitoring devices from a data store on the site or in acloud/remote/edge server, or in another appropriate manner.

In some implementations, the process variables of the steam turbinesystem include two or more of the following: turbine speed, turbineload, extraction or admission pressure or flow, inlet steam pressure orflow, and exhaust steam pressure or flow of the steam turbine system. Insome implementations, one of the two of the process variables of thesteam turbine system includes a turbine load or a turbine speed, andanother of the two of the process variables of the steam turbine systemincludes an extraction pressure or flow of the steam turbine system.

In some implementations, the three or more different operating pointscan include a known point (e.g., (0,0)) and two or more operating pointsmeasured under different operating conditions that reflect actualresponses or performances of the steam turbine system. A total of threeor more operating points are used for generating the steam performancemap.

At 520, coefficients of a steam performance map of the steam turbinesystem are calculated based on the measurements of each of the three ormore different operating points. The steam performance map represents afirst relationship between the position of the high-pressure controlvalve and the two of the process variables of the steam turbine system,and a second relationship between the position of the low-pressurecontrol valve and the two process variables of the steam turbine system.The first relationship and the second relationship can be linear ornonlinear. For example, Equation (1) shows an example of the firstrelationship between the position of the high-pressure control valve andthe two of the process variables of the steam turbine system; andEquation (2) shows an example of the second relationship between theposition of the low-pressure control valve and the two of the processvariables of the steam turbine system. The coefficients of a steamperformance map can include the ratio limiter coefficients (e.g.,constants K1-K6 in Equations (1) and (2)) of a ratio limiter of thecontroller.

In some implementations, the coefficients of the steam performance mapof the steam turbine system are calculated by curve fitting (includinglinear regression) or other statistic processing of the measurements ofeach of the three or more different operating points, according to thefirst relationship between the position of the high-pressure controlvalve and the two of the process variables of the steam turbine systemand the second relationship between the position of the low-pressurecontrol valve and the two of the process variables of the steam turbinesystem. Equations (7)-(12) show examples of calculating the coefficientsof the steam performance map of the steam turbine system.

At 530, the steam performance map of the steam turbine system isgenerated based on the coefficients. The steam performance map isgenerated, for example, by plotting, reconstructing, or otherwiserepresenting the first relationship between the position of thehigh-pressure control valve and the two of the process variables of thesteam turbine system and the second relationship between the position ofthe low-pressure control valve and the two of the process variables ofthe steam turbine system by plugging in the determined coefficients.

At 540, the steam turbine system is controlled based on the steamperformance map of the steam turbine system. In some implementations,controlling the steam turbine system based on the steam performance mapof the steam turbine system includes, for example, receiving currentvalues of the two process variables of the steam turbine system;determining a desired position of the high-pressure control valve and adesired position of the low-pressure control valve based on thecoefficients of the steam performance map of the steam turbine systemand the current values of the two process variables of the steam turbinesystem; outputting the desired position of the high-pressure controlvalve to an actuator coupled with the high-pressure control valve; andoutputting the desired position of the low-pressure control valve to anactuator coupled with the low-pressure control valve.

Some embodiments of subject matter and operations described in thisspecification can be implemented in digital electronic circuitry, or incomputer software, firmware, or hardware, including the structuresdisclosed in this specification and their structural equivalents, or incombinations of one or more of them. Some embodiments of subject matterdescribed in this specification can be implemented as one or morecomputer programs, i.e., one or more modules of computer programinstructions, encoded on computer storage medium for execution by, or tocontrol the operation of, data processing apparatus. A computer storagemedium can be, or can be included in, a computer-readable storagedevice, a computer-readable storage substrate, a random or serial accessmemory array or device, or a combination of one or more of them.Moreover, while a computer storage medium is not a propagated signal, acomputer storage medium can be a source or destination of computerprogram instructions encoded in an artificially generated propagatedsignal. The computer storage medium can also be, or be included in, oneor more separate physical components or media (e.g., multiple CDs,disks, or other storage devices).

The term “data processing apparatus” encompasses all kinds of apparatus,devices, and machines for processing data, including by way of example aprogrammable processor, a computer, a system on a chip, or multipleones, or combinations, of the foregoing. The apparatus can includespecial purpose logic circuitry, e.g., an FPGA (field programmable gatearray) or an ASIC (application specific integrated circuit). Theapparatus can also include, in addition to hardware, code that createsan execution environment for the computer program in question, e.g.,code that constitutes processor firmware, a protocol stack, a databasemanagement system, an operating system, a cross-platform runtimeenvironment, a virtual machine, or a combination of one or more of them.The apparatus and execution environment can realize various differentcomputing model infrastructures, such as web services, distributedcomputing and grid computing infrastructures.

A computer program (also known as a program, software, softwareapplication, script, or code) can be written in any form of programminglanguage, including compiled or interpreted languages, declarative orprocedural languages. A computer program may, but need not, correspondto a file in a file system. A program can be stored in a portion of afile that holds other programs or data (e.g., one or more scripts storedin a markup language document), in a single file dedicated to theprogram in question, or in multiple coordinated files (e.g., files thatstore one or more modules, sub programs, or portions of code). Acomputer program can be deployed to be executed on one computer or onmultiple computers that are located at one site or distributed acrossmultiple sites and interconnected by a communication network.

Some of the processes and logic flows described in this specificationcan be performed by one or more programmable processors executing one ormore computer programs to perform actions by operating on input data andgenerating output. The processes and logic flows can also be performedby, and apparatus can also be implemented as, special purpose logiccircuitry, e.g., an FPGA (field programmable gate array) or an ASIC(application specific integrated circuit).

Processors suitable for the execution of a computer program include, byway of example, both general and special purpose microprocessors, andprocessors of any kind of digital computer. Generally, a processor willreceive instructions and data from a read only memory or a random accessmemory, or both. A computer includes a processor for performing actionsin accordance with instructions and one or more memory devices forstoring instructions and data. A computer may also include, or beoperatively coupled to receive data from or transfer data to, or both,one or more mass storage devices for storing data, e.g., magnetic,magneto optical disks, or optical disks. However, a computer need nothave such devices. Devices suitable for storing computer programinstructions and data include all forms of non-volatile memory, mediaand memory devices, including by way of example semiconductor memorydevices (e.g., EPROM, EEPROM, flash memory devices, and others),magnetic disks (e.g., internal hard disks, removable disks, and others),magneto optical disks, and CD ROM and DVD-ROM disks. The processor andthe memory can be supplemented by, or incorporated in, special purposelogic circuitry.

To provide for interaction with a user, operations can be implemented ona computer having a display device (e.g., a monitor, or another type ofdisplay device) for displaying information to the user and a keyboardand a pointing device (e.g., a mouse, a trackball, a tablet, a touchsensitive screen, or another type of pointing device) by which the usercan provide input to the computer. Other kinds of devices can be used toprovide for interaction with a user as well; for example, feedbackprovided to the user can be any form of sensory feedback, e.g., visualfeedback, auditory feedback, or tactile feedback; and input from theuser can be received in any form, including acoustic, speech, or tactileinput. In addition, a computer can interact with a user by sendingdocuments to and receiving documents from a device that is used by theuser; for example, by sending web pages to a web browser on a user'sclient device in response to requests received from the web browser.

A client and server are generally remote from each other and typicallyinteract through a communication network. Examples of communicationnetworks include a local area network (“LAN”) and a wide area network(“WAN”), an inter-network (e.g., the Internet), a network including asatellite link, and peer-to-peer networks (e.g., ad hoc peer-to-peernetworks). The relationship of client and server arises by virtue ofcomputer programs running on the respective computers and having aclient-server relationship to each other.

A number of examples have been shown and described; variousmodifications can be made. While this specification contains manydetails, these should not be construed as limitations on the scope ofwhat may be claimed, but rather as descriptions of features specific toparticular examples. Certain features that are described in thisspecification in the context of separate implementations can also becombined. Conversely, various features that are described in the contextof a single implementation can also be implemented separately or in anysuitable sub-combination. Accordingly, other implementations are withinthe scope of the following claims.

1. A steam turbine system comprising: a high-pressure turbine section; alow-pressure turbine section; a high-pressure control valve operable toprovide an adjustable flow of steam into the high-pressure turbinesection; a low-pressure control valve operable to provide an adjustableflow of steam into the low-pressure turbine section; a controllerassociated with the high-pressure control valve and the low-pressurecontrol valve, the controller operable to: receive measurements of threeor more different operating points of the steam turbine system, themeasurements of each of the three or more different operating pointsincluding a position of the high-pressure control valve, a position ofthe low-pressure control valve, and two of process variables of thesteam turbine system; calculate coefficients of a steam performance mapof the steam turbine system based on the measurements of each of thethree or more different operating points, the steam performance maprepresenting a first relationship between the position of thehigh-pressure control valve and the two of the process variables of thesteam turbine system, and a second relationship between the position ofthe low-pressure control valve and the two of the process variables ofthe steam turbine system; and generate the steam performance map of thesteam turbine system based on the coefficients.
 2. The steam turbinesystem of claim 1, wherein the controller is further operable to:receive current values of the two of the process variables of the steamturbine system; determine a desired position of the high-pressurecontrol valve and a desired position of the low-pressure control valvebased on the coefficients of the steam performance map of the steamturbine system and the current values of the two of the processvariables of the steam turbine system; output the desired position ofthe high-pressure control valve to a first actuator coupled with thehigh-pressure control valve; and output the desired position of thelow-pressure control valve to a second actuator coupled with thelow-pressure control valve.
 3. The steam turbine system of claim 1,further comprising a plurality of sensors for measuring the two of theprocess variables of the steam turbine system.
 4. The steam turbinesystem of claim 1, wherein the process variables of the steam turbinesystem comprise two or more of the following: turbine speed, turbineload, extraction or admission pressure or flow, inlet steam pressure orflow, and exhaust steam pressure or flow of the steam turbine system. 5.The steam turbine system of claim 1, wherein the low-pressure turbinesection is a first low-pressure turbine section; and the low-pressurecontrol valve is a first low-pressure control valve, the steam turbinesystem comprising one or more low-pressure turbine sections in additionto the first low-pressure turbine section and one or more low-pressurecontrol valves in addition to the first low-pressure control valve. 6.The steam turbine system of claim 1, wherein the controller is operableto calculate the coefficients of a steam performance map of the steamturbine system by curve fitting the measurements of the three or moredifferent operating points.
 7. The steam turbine system of claim 1,wherein the steam turbine system operates in an extraction mode or anadmission mode.
 8. A method for generating a steam performance map of asteam turbine system, the steam turbine system comprising ahigh-pressure control valve, operable to provide an adjustable flow ofsteam fluid into a high-pressure turbine section, and a low-pressurecontrol valve operable to provide an adjustable flow of steam fluid intoa low-pressure turbine section, the method comprising: receiving, bydata processing apparatus, measurements of three or more differentoperating points of the steam turbine system, the measurements of eachof the three or more different operating points comprising a position ofthe high-pressure control valve, a position of the low-pressure controlvalve, and two of process variables of the steam turbine system;calculating, by the data processing apparatus, coefficients of a steamperformance map of the steam turbine system based on the measurements ofeach of the three or more different operating points, the steamperformance map representing a first relationship between the positionof the high-pressure control valve and the two of the process variablesof the steam turbine system, and a second relationship between theposition of the low-pressure control valve and the two of the processvariables of the steam turbine system; and generating, by the dataprocessing apparatus, the steam performance map of the steam turbinesystem based on the coefficients.
 9. The method of claim 8, furthercomprising controlling the steam turbine system based on the steamperformance map of the steam turbine system.
 10. The method of claim 9,wherein the controlling the steam turbine system based on the steamperformance map of the steam turbine system comprises: receiving currentvalues of the two process variables of the steam turbine system;determining a desired position of the high-pressure control valve and adesired position of the low-pressure control valve based on thecoefficients of the steam performance map of the steam turbine systemand the current values of the two process variables of the steam turbinesystem; outputting the desired position of the high-pressure controlvalve to an actuator coupled with the high-pressure control valve; andoutputting the desired position of the low-pressure control valve to anactuator coupled with the low-pressure control valve.
 11. The method ofclaim 8, further comprising: operating the steam turbine system at thethree or more different operating points; and for the each of the threeor more different operating points, measuring the position of thehigh-pressure control valve, the position of the low-pressure controlvalve, and the two of the process variables of the steam turbine system.12. The method of claim 8, wherein the process variables of the steamturbine system comprise two or more of the following: turbine speed,turbine load, extraction or admission pressure or flow, inlet steampressure or flow, and exhaust steam pressure or flow of the steamturbine system.
 13. The method of claim 8, wherein one of the two of theprocess variables of the steam turbine system comprises a turbine loador a turbine speed, and another of the two of the process variables ofthe steam turbine system comprises an extraction pressure or flow of thesteam turbine system.
 14. The method of claim 8, wherein the calculatingcoefficients of a steam performance map of the steam turbine systemcomprises calculating the coefficients of a steam performance map of thesteam turbine system by curve fitting the measurements of each of thethree or more different operating points.
 15. A non-transitorycomputer-readable medium storing instructions that, when executed bydata processing apparatus, perform operations for generating a steamperformance map of a steam turbine system that comprises a high-pressurecontrol valve operable to provide an adjustable flow of steam fluid intoa high-pressure turbine section and a low-pressure control valveoperable to provide an adjustable flow of steam fluid into alow-pressure turbine section, the operations comprising: receiving, bydata processing apparatus, measurements of three or more differentoperating points of steam turbine system, the measurements of each ofthe three or more different operating points including a position of thehigh-pressure control valve, a position of the low-pressure controlvalve, and two of process variables of the steam turbine system;calculating, by the data processing apparatus, coefficients of a steamperformance map of the steam turbine system based on the measurements ofeach of the three or more different operating points, the steamperformance map representing a first relationship between the positionof the high-pressure control valve and the two of the process variablesof the steam turbine system, and a second relationship between theposition of the low-pressure control valve and the two of the processvariables of the steam turbine system; and generating, by the dataprocessing apparatus, the steam performance map of the steam turbinesystem based on the coefficients.
 16. The non-transitorycomputer-readable medium of claim 15, wherein the operations furtherinclude controlling the steam turbine system based on the steamperformance map of the steam turbine system.
 17. The non-transitorycomputer-readable medium of claim 16, wherein the operations furtherinclude, wherein the controlling the steam turbine system based on thesteam performance map of the steam turbine system includes: receivingcurrent values of the two process variables of the steam turbine system;determining a desired position of the high-pressure control valve and adesired position of the low-pressure control valve based on thecoefficients of the steam performance map of the steam turbine systemand the current values of the two process variables of the steam turbinesystem; outputting the desired position of the high-pressure controlvalve to an actuator coupled with the high-pressure control valve; andoutputting the desired position of the low-pressure control valve to anactuator coupled with the low-pressure control valve.
 18. Thenon-transitory computer-readable medium of claim 15, wherein theoperations further include: operating the steam turbine system at thethree or more different operating points; and for the each of the threeor more different operating points, measuring the position of thehigh-pressure control valve, the position of the low-pressure controlvalve, and the two of the process variables of the steam turbine system.19. The non-transitory computer-readable medium of claim 15, wherein theprocess variables of the steam turbine system include two or more of thefollowing: turbine speed, turbine load, extraction or admission pressureor flow, inlet steam pressure or flow, and exhaust steam pressure orflow of the steam turbine system.
 20. The non-transitorycomputer-readable medium of claim 15, wherein the operations furtherinclude, wherein the calculating coefficients of a steam performance mapof the steam turbine system includes calculating the coefficients of asteam performance map of the steam turbine system by curve fitting themeasurements of each of the three or more different operating points.